CHAPTERXI.Section 68.AT 28 Minutes past II. the solid Weights before mentioned were thrown out.At 29 Minutes the Barometer had fallen to 25 Inches.Balloon reascending.A Handful of Feathers were sent adrift, which fell quick: demonstratinglikewisethe Ascent of the Balloon, a second Time: but, tho’ 12 Pounds lighter, it did not seem to regain its original Height: judgingmerelyfrom this Circumstance, that no more Gass escapedvisiblyfrom the Mouth.Apparent Size and Situation of thewhiteFlag.69. It is somewhat remarkable, that, on repeated Enquiries from unprejudiced Persons, thewhiteFlag, when suspended from the Car above 440 Yards, appeared 4 Yards long: andwhen at the end of thehalf MileTwine, seemed about 8 Yards long, to Spectators from below, in different Places: that sometimes it appeared before, and sometimes behind the Balloon: while to the Observer in the Car, it seemed regularly to follow the Balloon: unless when anewMotion was impressed upon the latter: at which Time thewhiteFlag was situated almost under the Car: or when the Balloon changed its Direction; the Flag beingthennot alwaysdiscoverable.When seenedgewiseorforeshortened; it woudappearto benearerthe Car than it really was.Effect of thewhiteFlag on the Balloon.70. As there was a Peculiarity attending the Situation of thehalf MileFlag, which may prove of singular Use in Airostation; it ought not to be passed over in Silence.The half Mile Flag hanging loosely from the Car; not perpendicularly under, but following it, frequently atan Angle of about 45 Degrees; shews that the Flag met a Resistance from the Air, unfelt by the Balloon: which out strip’d it, in Proportion to thegreaterSurface which the Balloon exposed to the Wind.Taking also into the Account, that the Balloon remained in Equilibrio; while the Flag was subject to the Force of Gravity: which Force was restrained from Exertion, otherwise than as aVis Inertiæ, to keep it always in a perpendicular Situation.The Resistance of the Air, acting in an horizontal Direction against theVis Inertiæof the Flag, must have a Tendency to drive it back: which being ineffectual; the Flag must consequentlyrise; and in risingwill retard the Balloon.A Power may therefore be communicated to a Balloon, in the Direction of the Wind, which shallretardits Progress throu’ the Air: a Subjectwhich seems capable of farther Prosecution.
CHAPTERXI.
Section 68.AT 28 Minutes past II. the solid Weights before mentioned were thrown out.
At 29 Minutes the Barometer had fallen to 25 Inches.
Balloon reascending.
A Handful of Feathers were sent adrift, which fell quick: demonstratinglikewisethe Ascent of the Balloon, a second Time: but, tho’ 12 Pounds lighter, it did not seem to regain its original Height: judgingmerelyfrom this Circumstance, that no more Gass escapedvisiblyfrom the Mouth.
Apparent Size and Situation of thewhiteFlag.
69. It is somewhat remarkable, that, on repeated Enquiries from unprejudiced Persons, thewhiteFlag, when suspended from the Car above 440 Yards, appeared 4 Yards long: andwhen at the end of thehalf MileTwine, seemed about 8 Yards long, to Spectators from below, in different Places: that sometimes it appeared before, and sometimes behind the Balloon: while to the Observer in the Car, it seemed regularly to follow the Balloon: unless when anewMotion was impressed upon the latter: at which Time thewhiteFlag was situated almost under the Car: or when the Balloon changed its Direction; the Flag beingthennot alwaysdiscoverable.
When seenedgewiseorforeshortened; it woudappearto benearerthe Car than it really was.
Effect of thewhiteFlag on the Balloon.
70. As there was a Peculiarity attending the Situation of thehalf MileFlag, which may prove of singular Use in Airostation; it ought not to be passed over in Silence.
The half Mile Flag hanging loosely from the Car; not perpendicularly under, but following it, frequently atan Angle of about 45 Degrees; shews that the Flag met a Resistance from the Air, unfelt by the Balloon: which out strip’d it, in Proportion to thegreaterSurface which the Balloon exposed to the Wind.
Taking also into the Account, that the Balloon remained in Equilibrio; while the Flag was subject to the Force of Gravity: which Force was restrained from Exertion, otherwise than as aVis Inertiæ, to keep it always in a perpendicular Situation.
The Resistance of the Air, acting in an horizontal Direction against theVis Inertiæof the Flag, must have a Tendency to drive it back: which being ineffectual; the Flag must consequentlyrise; and in risingwill retard the Balloon.
A Power may therefore be communicated to a Balloon, in the Direction of the Wind, which shallretardits Progress throu’ the Air: a Subjectwhich seems capable of farther Prosecution.